1. Field of the Invention
The present invention relates generally to the fields of neurology, immunology and protein chemistry. More specifically, the present invention relates to uses of oral Type I interferons to inhibit transplant rejection.
2. Description of the Related Art
Type I diabetes is a chronic disorder that results from autoimmune destruction of the insulin-producing pancreatic xcex2 cell. In the United States, the prevalence of type I diabetes by age 20 years is 0.26% and lifetime prevalence approaches 0.40%; thus approximately 1.5 million Americans have type I diabetes [1]. Once type I diabetes patients become insulin dependent, there is little therapeutic options except insulin replacement.
The Relevance of the NOD Mouse Model to Diabetes Mellitus:
The NOD mouse is a model of the human autoimmune disease type I diabetes [2-4]. The NOD mouse model is presumed to be T cell subset mediated and dependent on inflammatory cytokines for disease expression. Many key features of human type I diabetes are reflected in the NOD mouse: the development of insulinitis with infiltration of lymphocytes into the pancreatic islets of Langerhans that are selectively cytotoxic to the insulin producing xcex2 cells; the dependence of disease pathogenesis by T cells; and transmission of type I diabetes by hematopoietic cells in bone marrow [5-9].
Immunoregulatorv Cytokine Imbalances in Type I Diabetes:
Destruction of islet cells in NOD mice has been associated with a subset of T cells producing IFN-xcex3 [17]. IFN-xcex3 has been detected in lymphocytes infiltrating islets of human subjects with recent onset type I diabetes [18] and antibodies against IFN-xcex3 protect against diabetes development in NOD mice [19, 20] and BB rats [21]. IFN-xcex3 transgenic mice develop type I diabetes with inflammatory destruction of the islets [22, 23]. The incidence of type I diabetes correlates with IFN-xcex3-producing islet T cells in NOD [24] and in NOD.scid mice [25]. This suggests that intraislet IFN-xcex3 may be critical in the development of diabetes mellitus (DM).
IFN-xcex1 has been detected in xcex2 cells of animals and human subjects with recent onset type I diabetes [26, 27] and may elicit an immune mediated destruction of xcex2 cells; anti-IFN-xcex1 antibody prevents this xcex2 cell damage [28]. Islet expression of IFN-xcex1, induced by polyinosinic-polycytidylic acid {poly (I:C)} or expressed from a transgene, precedes diabetes in both the BB rat and streptozotocin (STZ)-treated mice [29]. However, IFNs are well known to have dose related opposing effects on immune responses. In contrast to the results above, poly (I:C) can protect against overt type I diabetes in the NOD mouse [30] and can prevent the development of diabetes in BB rats by interfering with the development of insulitis [31]. Parenteral IFN-xcex1 can decrease the development of spontaneous diabetes, the passive transfer of diabetes in NOD mice and decrease islet inflammation [32]. Therefore, IFN-xcex1 is not intrinsically diabetogenic and may be protective. Indeed, moderate amounts of intraislet IFN-xcex1 may be anti-inflammatory.
IL-4 and IL-10 cytokines can protect against the development of type I diabetes in the NOD mouse [33]. Transgenic NOD-IL-4 and rIL-4 administration to prediabetic NOD mice is protective against type I diabetes [34, 35], whereas the impairment of IL-4 production by PBMC or T cells was found in type I diabetes patients at diabetes onset [36]. IL-10 delays the onset of disease and reduces the incidence of diabetes, the severity of insulitis, prevents cellular infiltration of islet cells, and promotes normal insulin production by xcex2 cells [37, 38].
Adoptive Transfer of Protection Against Allograft Islet Rejection:
CD8+ cytotoxic T cell lines and clones generated from lymphocytic islet infiltrates can transfer diabetes rapidly without CD4+ T cells [42]. Islet-infiltrating lymphocytes from prediabetic SCD mice rapidly transfer diabetes to NOD.scid mice; cotransfer of splenocytes or CD4+, but not CD8+ spleen cells, together with islet infiltrating lymphocytes from prediabetics delayed the rapid transfer of type I diabetes, suggesting CD4+ cells also mediate immunoregulation [43, 44]. CD4+ T cell clones from unprimed NOD mice can protect against adoptive transfer of DM [45].
The effect of pro-inflammatory (IL-1, IL-2, IL-6, TNF-xcex1, type II IFN IFN-xcex3) and anti-inflammatory (IL-4, IL-10, IFN-xcex1) cytokines in experimental models of allograft islet transplantation has been investigated. Enhanced expression of pro-inflammatory type II IFN-xcex3 contribute to graft destruction [48]. Pro-inflammatory cytokines IL-1xcex2, TNF-xcex1, and IFN-xcex3 are cytotoxic to human islet 0-cells in vitro [49]. Non-function of isologous and allogeneic islet grafts is prevented by treatment with or increased IL-4 and IL-10 and decreased type II IFN IFN-xcex3 [33, 50]. Inhibition of NF-xcexaB suppresses immune-mediated cell death in xcex2-cells and protects from diabetogenic T cell immune attack in vivo. Therefore, increased IL-4/IL-10, inhibition of IFN-xcex3 and NF-xcexaB activation may protect pancreatic xcex2-cells [51].
Rejecting islet allografts contain a mixture of pro-inflammatory and anti-inflammatory cytokines such as IL-2 and IFN-xcex3 mRNA transcripts [52] and increased expression of IL-2, IL-4, TNF-xcex1, IFN-xcex3 and IL-10 mRNAs at the peak of the cellular infiltrate (on day 5) in islet allografts [53]. Allogeneic islet grafts showed increased IL-1 from 1 to 7 days, IL-2 and IFN-xcex3 transcripts at 1, 3, 5, and 7 days with a peak at day 5, IL-6 expression at 1 day, with constant IL-10 at all time points [54]. ICAM-1 antisense oligonucleotides can decrease increased IL-1 mRNA expression following kidney capsule islet transplantation and prolong allograft islet survival [55]. However, the simple Th1 to Th2 immune deviation does not blunt the severity of MHC-mismatched allograft rejection [50].
Type I Interferons:
In 1957 Isaacs and Lindenmann described a factor (interferon) produced by virus infected cells with rapid antiviral activity [57]. Type I IFNs are composed of two highly homologous proteins IFN-xcex1 (leucocyte IFN) and IFN-xcex2 (fibroblast IFN) with similar biological properties [58], interact with the same cell receptor [59], and resist stomach acidity. Fifty to two hundred high affinity type I receptors are found on all lymphoid cells, including the gut associated lymphoid tissue (GALT) [60-62]. Therefore, type I IFNs are immunoactive endogenously produced proteins that can be active in the gut. Systemic effects may be achieved with IFN-xcex2 administered directly to the upper GI tract in experimental animal models of auto-immune disease and human auto-immune disease [63, 64] and does not result in detectable levels of IFN-xcex1 in the blood [65-68] nor xcex22-microglobulin, neopterin, or 2-5A synthetase protein arkers of IFN absorption [69].
GALT (Gut Associated Lymphoid Tissue):
The afferent gut-associated lymphoid tissue has multiple types of constituent immune cells in lymphoid nodules termed Peyer""s patches (PP) [78]. Peyer""s patches contain T lymphocytes that are predominantly composed of the CD14+ T cells [79, 80] where regulatory cells can be generated [81, 82]. GALT activated lymphocytes, by virtue of their ability to circulate through the body, potentially can transfer their biological activities widely in the absence of circulating cytokines after contacting type I IFN in the gut-associated lymphoid tissue [83-87]. At their destination (islets), type I IFN-activated cells may release anti-inflammatory type I IFNs which are able to inhibit neighboring inflammatory cells by paracrine cytokine release.
Islet transplantation:
Islet transplants possess significantly potential advantages over whole-gland transplants because it is a simple procedure with only small risk, may achieve insulin-independence [88], has clear advantages over exogenous insulin therapy but limited success to date [89]. However, type I diabetes is characterized by the presence of an autoimmune memory. This recurrence of autoimmunity is partly responsible for the need of extensive immunosuppression in islet transplantation in type I diabetes [90].
The effect of pro-inflammatory and anti-inflammatory cytokines in experimental models of allograft islet transplantation has been investigated. Enhanced expression of pro-inflammatory Type II IFN-xcex3 contribute to graft destruction [48]. Rejection of isologous and allogeneic islet grafts is prevented by treatment with or increased IL-4 and IL-10 and decreased type II IFN-xcex3 [33, 50]. Inhibition of NF-xcexaKB suppresses immune-mediated cell death in xcex2-cells and protects from diabetogenic T cell immune attack in vivo. Therefore, increased IL-4/IL-10 and inhibition of NF-xcexaB may protect pancreatic xcex2-cells [51].
Currently used immunosuppressant agents are either toxic or cannot prevent the spontaneous onset of DM. Cyclosporine, prednisone, azathioprine, and FK506 are toxic to islet cells [91-96]. 15-deoxyspergualin prolongs allograft islet survival, but high doses do not prevent rejection indefinitely and are toxic [97, 98]. Leflunomide has no apparent toxicities in mice, but does not significantly reduced the incidence of spontaneous diabetes in NOD mice, in distinct contrast to ingested murine IFN-xcex1 [99]. Oral mycophenolate mofetil, an antiproliferative agent, does not prevent allograft rejection at day +30 [100] and does not block islet graft rejection in spontaneously diabetic BB rats [101]. In pig islet allografts, a combination of cyclosporine, azathioprine, and prednisolone, 15-deoxyspergualin, and antithymocyte globulin was successful. However, this immunosuppressive protocol resulted in a high rate of infectious complications [94].
The prior art is deficient in the lack of effective means to treat transplant rejection by using oral type I interferons. The present invention fulfills this long-standing need and desire in the art.
The present invention is directed to a non-toxic method to treat or even prevent organ transplant rejection by using oral type I interferons. In one embodiment of the present invention, there is provided a method of treating transplant rejection in an animal by orally administering a type one interferon, wherein the type one interferon is ingested after oral administration. Preferably, the type one interferon is alpha-interferon or beta-interferon. More preferably, the interferon is selected from the group consisting of human recombinant interferon, rat interferon and murine interferon.
In another embodiment of the present invention, there is provided a method of preventing transplant rejection in an animal by orally administering a type one interferon, wherein the type one interferon is ingested after oral administration.
In another embodiment of the present invention, there is provided a method of preventing transplant rejection in an animal, comprising the step of administering a type one interferon to said animal.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the presently preferred embodiments of the invention given for the purpose of disclosure.